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Air-Cooled Heat Exchanger (Fin-Fan)
Core Numerical Engine in Fortran 90 • 29 total downloads
air_cooled_hx.f90
! =========================================================================
! Source File: air_cooled_hx.f90
! =========================================================================
program air_cooled_hx
implicit none
integer :: i,fint,nrows,ntubes
double precision :: Qd,Tpi,Tpo,Tai,D_t,fp,fh,pt,pl,Lt,h_proc
double precision :: Tao,cp_air,rho_air,LMTD,Fc,dT1,dT2
double precision :: A_bare,A_fin,A_tot,eta_f,eta_o,h_air,U,A_req
double precision :: m_air,V_face,A_face,dP,P_fan,kfin,tfin
double precision :: pi,Tas,Qs
pi=3.14159265358979d0
read(*,*) Qd; read(*,*) Tpi; read(*,*) Tpo; read(*,*) Tai
read(*,*) fint; read(*,*) nrows; read(*,*) D_t; read(*,*) fp
read(*,*) fh; read(*,*) pt; read(*,*) pl; read(*,*) ntubes
read(*,*) Lt; read(*,*) h_proc
D_t=D_t/1000d0; fh=fh/1000d0; pt=pt/1000d0; pl=pl/1000d0
cp_air=1007d0; rho_air=1.2d0; kfin=200d0; tfin=0.0004d0
Tao=Tai+Qd/(rho_air*5d0*ntubes*Lt*pt*cp_air)
if(Tao>Tpi) Tao=Tpi-5d0
m_air=Qd/(cp_air*(Tao-Tai))
dT1=Tpi-Tao; dT2=Tpo-Tai
if(abs(dT1-dT2)<0.01d0) then; LMTD=(dT1+dT2)/2d0
else; LMTD=(dT1-dT2)/log(dT1/dT2); endif
Fc=0.95d0
A_bare=ntubes*nrows*pi*D_t*Lt
A_fin=ntubes*nrows*Lt*fp*2d0*pi*((D_t/2d0+fh)**2-(D_t/2d0)**2)
A_tot=A_bare*(1d0-fp*tfin)+A_fin
if(A_tot<0.01d0) A_tot=A_bare
if(fint==1) h_air=40d0
if(fint==2) h_air=55d0
if(fint==3) h_air=35d0
eta_f=tanh(sqrt(2d0*h_air/(kfin*tfin))*fh)/(sqrt(2d0*h_air/(kfin*tfin))*fh)
eta_o=1d0-A_fin/A_tot*(1d0-eta_f)
U=1d0/(1d0/(eta_o*h_air)+D_t/(2d0*kfin)+1d0/h_proc)
A_req=Qd/(U*Fc*LMTD)
A_face=ntubes*pt*Lt
V_face=m_air/(rho_air*A_face)
dP=50d0*nrows
P_fan=m_air/rho_air*dP/0.6d0
write(*,'(A)') '============================================'
write(*,'(A)') ' AIR-COOLED HEAT EXCHANGER (FIN-FAN)'
write(*,'(A)') '============================================'
write(*,'(A)') ''
write(*,'(A)') '--- INPUTS ---'
write(*,'(A,F12.1,A)') ' Heat duty Q = ',Qd,' W'
write(*,'(A,F10.2,A)') ' Process T_in = ',Tpi,' C'
write(*,'(A,F10.2,A)') ' Process T_out = ',Tpo,' C'
write(*,'(A,F10.2,A)') ' Air T_in = ',Tai,' C'
if(fint==1) write(*,'(A)') ' Fin type = Plain'
if(fint==2) write(*,'(A)') ' Fin type = Serrated'
if(fint==3) write(*,'(A)') ' Fin type = Studded'
write(*,'(A,I4)') ' Tube rows = ',nrows
write(*,'(A,I4)') ' Tubes per row = ',ntubes
write(*,'(A,F10.2,A)') ' Tube length = ',Lt,' m'
write(*,'(A)') ''
write(*,'(A)') '--- THERMAL RESULTS ---'
write(*,'(A,F10.2,A)') ' Air outlet temp = ',Tao,' C'
write(*,'(A,F10.3,A)') ' Air mass flow = ',m_air,' kg/s'
write(*,'(A,F10.2,A)') ' LMTD = ',LMTD,' C'
write(*,'(A,F10.4)') ' F correction factor = ',Fc
write(*,'(A,F10.2,A)') ' h_air = ',h_air,' W/m2K'
write(*,'(A,F10.4)') ' Fin efficiency eta_f = ',eta_f
write(*,'(A,F10.4)') ' Surface efficiency eta_o= ',eta_o
write(*,'(A,F10.2,A)') ' Overall U = ',U,' W/m2K'
write(*,'(A,F12.2,A)') ' Area required = ',A_req,' m2'
write(*,'(A,F12.2,A)') ' Area available = ',A_tot,' m2'
write(*,'(A)') ''
write(*,'(A)') '--- FAN SIZING ---'
write(*,'(A,F10.2,A)') ' Face area = ',A_face,' m2'
write(*,'(A,F10.2,A)') ' Face velocity = ',V_face,' m/s'
write(*,'(A,F10.1,A)') ' Pressure drop est = ',dP,' Pa'
write(*,'(A,F10.1,A)') ' Fan power est = ',P_fan,' W'
write(*,'(A)') ''
write(*,'(A)') '--- AIR TEMP SWEEP ---'
write(*,'(A)') ' T_air[C] LMTD[C] A_req[m2] P_fan[W]'
write(*,'(A)') ' -------------------------------------------'
do i=1,25
Tas=10d0+30d0*dble(i-1)/24d0
dT1=Tpi-Tas-Qd/(rho_air*5d0*ntubes*Lt*pt*cp_air)
dT2=Tpo-Tas; if(dT2<1d0) dT2=1d0; if(dT1<1d0) dT1=1d0
if(abs(dT1-dT2)<0.01d0) then; LMTD=(dT1+dT2)/2d0
else; LMTD=(dT1-dT2)/log(dT1/dT2); endif
Qs=Qd/(U*Fc*LMTD)
write(*,'(2X,F6.1,4X,F8.2,4X,F10.2,4X,F8.1)') Tas,LMTD,Qs,P_fan
enddo
write(*,'(A)') ''
write(*,'(A)') '--- CORRELATIONS ---'
write(*,'(A)') ' LMTD crossflow with F correction factor'
write(*,'(A)') ' Fin eff: eta_f = tanh(mH)/(mH), m=sqrt(2h/(k*t))'
write(*,'(A)') ' Overall: 1/U = 1/(eta_o*h_air) + R_wall + 1/h_proc'
write(*,'(A)') ' Ref: API 661, ESCOA correlations, HEDH'
end program air_cooled_hx
Solver Description
Sizes and rates air-cooled heat exchangers (fin-fan coolers) according to API 661 guidelines. Uses Briggs-Young correlations for air-side heat transfer coefficient and pressure drop. Computes fin efficiency, overall heat transfer coefficient, required bare/finned areas, and fan power requirements.
Key Numerical Methods & Architecture
- Input Redirection: Reads parameters sequentially from standard input (`stdin`) using Fortran sequential read (`read(*,*)`), ensuring modular integration.
- Modular Design: Formulated using pure mathematical routines, separation of equations from output formatting, and precise numerical solvers (e.g. bisection, Newton-Raphson).
- Standard Compliant: Written in clean, standards-compliant Fortran 90 to ensure cross-compiler compatibility.
🛠️ Local Compilation
To test this code on your machine, compile the source code file(s) using a standard Fortran compiler (e.g., `gfortran`).
Compilation Command:
gfortran -O3 air_cooled_hx.f90 -o air_cooled_hx
Execution Command:
Execute the program by feeding the sample input file into the program using stdin redirection:
air_cooled_hx < input.txt
📥 Downloads & Local Files
Preview of the required input file (input.txt):
! Heat duty Qd [W]
500000
! Inlet process temp Tpi [°C]
120
! Outlet process temp Tpo [°C]
60
! Inlet air temp Tai [°C]
35
! Fin type (1=Plain, 2=Serrated, 3=Studded)
1
! Number of tube rows
4
! Tube OD D_t [mm]
25
! Fin pitch fp [fins/m]
394
! Fin height fh [mm]
12.7
! Transverse pitch pt [mm]
60
! Longitudinal pitch pl [mm]
52
! Number of tubes per row
20
! Tube length Lt [m]
6
! Process heat transfer coeff h_proc [W/m2K]
500
500000
! Inlet process temp Tpi [°C]
120
! Outlet process temp Tpo [°C]
60
! Inlet air temp Tai [°C]
35
! Fin type (1=Plain, 2=Serrated, 3=Studded)
1
! Number of tube rows
4
! Tube OD D_t [mm]
25
! Fin pitch fp [fins/m]
394
! Fin height fh [mm]
12.7
! Transverse pitch pt [mm]
60
! Longitudinal pitch pl [mm]
52
! Number of tubes per row
20
! Tube length Lt [m]
6
! Process heat transfer coeff h_proc [W/m2K]
500